Loading ...
Sorry, an error occurred while loading the content.

1192Re: tropical degrees for Magellanic Clouds

Expand Messages
  • mahtezcatpoc
    Dec 31, 2005
    • 0 Attachment
      --- In thefixedstars@yahoogroups.com, "Diana K. Rosenberg"
      <ye-stars@i...> wrote:
      >
      > Date: Thu, 29 Dec 2005 23:08:13 -0800 (PST)
      > From: Mark Andrew Holmes <mahtezcatpoc@y...>
      > Subject: The Magellanic Clouds
      >
      > Mark wrote:
      >
      > If anybody can give us Tropical longitude ranges for
      > Nubecula Major (the Large Magellanic Cloud) and
      > Nubecula Minor (the Small Magellanic Cloud) since
      > 1900, I would appreciate it. Vivian Robson has them at
      > 4 Gemini to 0 Cancer and 15 Aries to 4 Taurus,
      > respectively. I'm sure that's changed since he
      > published *The Fixed Stars and Constellations in
      > Astrology.* Robson doesn't give minute values, either,
      > just the degrees.
      >
      > Hi Mark,
      >
      > I do not have anything "official" - but using the illustrations
      > in Staal's The New Patterns in the Sky (pp 243-245), I would
      > say that the Large Magellanic Cloud (in Dorado/Mensa) runs
      > from approx RA 4.6 to 6.5, and from about Declination -65 to -73,
      > and the Small Magellanic Cloud (in Tucana) from approx
      > RA 0.4 - 1.4, Declination -72 to -77.
      >
      > Converting these figures to tropical degrees, epoch 2000, I ran into
      > trouble with the Larger Cloud, because it is in Dorado/Mensa, right
      at the
      > South Pole of the Ecliptic! Lines of Celestial Longitude (i.e. tropical
      > degrees) all run together at that point; so even a small difference in
      > (Equatorial) RA and Declination becomes a HUGE difference when
      projected
      > up on to the Ecliptic.


      Yeah.


      >
      > I used Bernadette's Starlight Program and used Lincoln's chart
      (because he
      > had stuff in Aquarius and Aries), then set it to zoom out so that
      the sky
      > could be viewed as a globe, and set it to show (in the southern sky)
      > both the lines of Right Ascension (Equator-based) and lines of celestial
      > longitude (Ecliptic based).
      >
      > That's when I saw the problem (it looks like 2 rival spider webs
      > interfering with each other!).
      >
      > If you want, I can scan it and send it as an attachment so you can
      see the
      > problem.




      Okay.




      >
      > Using Mark Pottenger's conversion program (Mark has a
      > degree in astronomy) here are the results for the LMC:
      >
      > RA 4.6 at Dec 73 South: 8 Aquarius 53
      > RA 6.1 at Dec 73 South: 26 Sagittarius 06
      > RA 4.6 at Dec 65 South: 0 Aries 34
      > RA 6.1 at Dec 65 South: 22 Cancer 12
      >
      > The Smaller Cloud, in Tucana (just north of Octans, the South
      > Pole of the EQUATOR), is easier:
      >
      > RA 0.4 at Dec 72 South: 11 Aquarius 24
      > RA 1.4 at Dec 72 South: 16 Aquarius 12
      > RA 0.4 at Dec 77 South: 1 Aquarius 26
      > RA 1.4 at Dec 77 South: 3 Aquarius 48
      >
      > So you see that the Smaller Cloud runs from (very approximately)
      > 1 to 16 Aquarius; but the Larger Cloud runs, in tropical terms,
      > from 26 Sag to 22 Cancer, a span of 206 degrees!

      Meaning that if you were to use ranges, just about everybody would
      have something on Nubecula Major.

      Okay.


      >
      > This is why it makes more sense to just work with the "center" of
      > these 2 clouds:
      >
      > In:
      >
      > http://www.daviddarling.info/encyclopedia/L/LMC.html
      > http://www.ebicom.net/~rsf1/fun/sm-cmts.htm:
      > The coordinates given for the Large Magellanic Cloud are:
      > Equatorial - RA 05 hrs 23.6 min, Dec -69 deg 45 min
      > Which gives: 12 Aquarius 33
      > But:
      > http://www.atnf.csiro.au/research/smc_h1/get_spectrum.html
      > has, for the 2 clouds: (centered at) 05 20, -68 44 and 01 01, -72 56
      > Which gives:
      > 25 Aquarius 42 for the LMC, 12 Aquarius 28 for the SMC
      > A headache, for sure. Lord only knows where Robson got his results.


      Okay, so if you can't get a definitive position for the center of the
      LMC (and anybody's "definitive position" might be controversial), then
      there's not much point in using it at all, is there?

      Mark A. Holmes
    • Show all 2 messages in this topic